Single chip microprocessors have been increasing in their basic clock rate so that a 25 MHz clock rate is no longer considered unusually high. During each consecutive clock cycle, a different step in the arithmetic functions performed by the microprocessor is carried out. Microinstructions consisting of a word containing multiple binary bits, are consecutively applied to the control input of the arithmetic logic in a microprocessor, one word for each consecutive cycle of arithmetic operation. These microinstructions must be read from a microinstruction storage unit such as a writable random access memory or a read only memory which is capable of an access cycle time which is at least as fast as the arithmetic cycle time for the arithmetic logic of the microprocessor. Thus, for arithmetic logic operating at a 25 MHz rate, a 40 nanosecond access cycle time is required in order to read consecutive words from the microinstruction storage. Although bipolar transistor writable random access memories are available which are capable of such short access cycle times, it is difficult to fabricate a field effect transistor writable random access memory on the same integrated circuit chip with the arithmetic logic of the microprocessor, which is capable of sustaining such short memory access cycle times.